scholarly journals Abundance, seasonality and size of Atlantic salmon smolts entrained on power station intake screens in the Severn Estuary

1994 ◽  
Vol 74 (3) ◽  
pp. 527-534 ◽  
Author(s):  
P.N. Claridge ◽  
I.C. Potter
Keyword(s):  
Atlantic Salmon ◽  
Standard Length ◽  
Condition Factor ◽  
Early Summer ◽  
Length Frequency ◽  
Power Station ◽  
Severn Estuary ◽  
Frequency Distributions ◽  
The Mean ◽  
One Year

Atlantic salmon smolts were sampled from the intake screens of the Oldbury power station in the inner Severn Estuary at weekly intervals between July 1972 and June 1977. These catches, and those taken over nearly three years from the nearby Berkeley power station, demonstrated that the abundance of smolts in the estuary peaked in autumn (October) and, to a far greater extent, in spring (April and May). However, small numbers of smolts were occasionally found in all other months of the year except July. Standard length-frequency distributions of smolts remained unimodal throughout the year. Lengths ranged from 76 to 187 mm, mean 130·2 ±1·87 mm (95% CL), and wet weights ranged from 5·4 to 68·0 g, mean 26·9 ±1·17 g. The mean monthly standard length of smolts increased slightly between the autumn of one year and the spring/early summer of the next year, suggesting that, on average, the former were six months younger than the latter. The condition factor was significantly greater in autumn (1·40) than in spring (1·23). It is estimated that the total number of salmon smolts entrained annually on the screens at Oldbury during the five years ranged from 92 to 791, with a mean of 405. Total estimated numbers at Berkeley ranged from 196 to 788 per annum. The numbers at Oldbury are lower than those estimated for the downstream migrants of the Twaite shad, another anadromous species, and far lower than those of the most abundant of the marine fish species that use the Severn Estuary as a nursery area.

scholarly journals Movements, abundance, age composition and growth of bass, Dicentrarchus labrax, in the Severn Estuary and inner Bristol Channel

1983 ◽  
Vol 63 (4) ◽  
pp. 871-879 ◽  
Author(s):  
P. N. Claridge ◽  
I. C. Potter
Keyword(s):  
Standard Length ◽  
Dicentrarchus Labrax ◽  
Age Classes ◽  
Power Station ◽  
Age Composition ◽  
Severn Estuary ◽  
Late Autumn ◽  
The Mean ◽  
Peak Abundance ◽  
Autumn And Winter

The movements, abundance, age composition and growth of bass, Dicentrarchus labrax (L.), in the Severn Estuary and inner Bristol Channel have been described from regular samples offish taken from power-station intake screens between 1972 and 1977. Bass began to move into the estuary during late August or September and reached peak abundance between September and early November. The tendency for fish to move seawards in the late autumn and winter may be related to declining water temperatures in the estuary. Likewise, differences in abundance between years appear to be related to annual differences in temperature. Although the populations were dominated by the 0 + age class, successively decreasing numbers of the next four age classes and occasional 5 + fish were also present. Respective mean standard lengths of bass in the estuary at the end of their first to fifth years of life were approximately 65 mm (≡ 4·5 g), 130 mm (≡ 37·9 g), 190 mm (≡ 121·1 g), 250 mm (≡ 280·4 g) and 290 mm (≡ 441.5 g). Growth occurred predominantly between May and September, with the mean standard length of 1 + fish increasing from approximately 65 mm (≡ 4·5 g) to 130 mm (≡ 37·9 g).

Reference points for the length-based indicator Lmax5% for use in the assessment of data-limited stocks

2019 ◽  
Vol 76 (7) ◽  
pp. 2125-2139 ◽  
Author(s):  
Tanja Miethe ◽  
Yves Reecht ◽  
Helen Dobby
Keyword(s):  
Life Histories ◽  
Stock Assessment ◽  
Reference Points ◽  
Length Frequency ◽  
Frequency Distributions ◽  
Simulation Tools ◽  
Spawning Potential Ratio ◽  
The Mean ◽  
Commercial Sources ◽  
Length Frequency Data

Abstract In the absence of abundance indices from scientific surveys or commercial sources, reliable length frequency data from sampled commercial catches can be used to provide an indirect assessment of fishing mortality. Length-based indicators are simple metrics which describe length frequency distributions. The length-based indicator Lmax5%, the mean length of the largest 5% of individuals in the catch, combined with appropriately selected reference points, can be used to evaluate the presence of very large individuals in the catch and hence determine exploitation level. Using analytical per-recruit models, we derive reference points consistent with a spawning potential ratio of 40%. The reference points depend on the life history parameters for natural mortality, maturity, and growth (M, Lmat, L∞, k, CVL∞). Using available simulation tools, we investigate the sensitivity of the reference points to errors in these parameters and explore the usefulness of particular reference points for management purposes for stocks with different life histories. The proposed reference points are robust to uncertainty in length at first capture, Lc, and take into account the maturation schedule of a species. For those stocks with high M/k ratios (>1), Lmax5%, combined with the appropriate reference point, can be used to provide a data-limited stock assessment.

A METHOD FOR SEPARATING BIMODAL LENGTH FREQUENCY DISTRIBUTIONS IN JUVENILE ATLANTIC SALMON POPULATIONS

1989 ◽  
Vol 69 (3) ◽  
pp. 613-617 ◽  
Author(s):  
I. McMILLAN ◽  
J. K. BAILEY ◽  
G. W. FRIARS ◽  
M. QUINTON ◽  
A. R. HANKE
Keyword(s):  
Atlantic Salmon ◽  
Distribution Data ◽  
Length Frequency ◽  
Frequency Distributions ◽  
Juvenile Atlantic Salmon ◽  
Population Distributions ◽  
Multimodal Distributions ◽  
Recent Developments ◽  
Mean And Variance ◽  
Key Words Fish

Growth studies on fish populations are often complicated by the presence of bimodality in the data. Traditional parametric tests are not applicable in these circumstances and familiar statistics such as mean and variance become difficult to interpret. Recent developments in catastrophe theory allow a new approach to working with multimodal distributions which provides specific parameters that have particular biological meaning. This paper presents an application of the nonmixture multimodal probability density function to length frequency distribution data collected on juvenile Atlantic salmon at the Atlantic Salmon Federation hatchery in St. Andrews, New Brunswick during the fall of 1982. The model was found to be a useful tool for describing the bimodal distributions and provided a set of parameters that can serve as a basis by which different population distributions can be compared. Key words: Fish breeding, bimodal distributions

scholarly journals Some Aspects of Biology of Chola Punti Puntius Chola (Hamilton) from the Kangsa River

1970 ◽  
Vol 45 (4) ◽  
pp. 309-314
Author(s):  
Bi K Saha ◽  
A Saha
Keyword(s):  
Sex Ratio ◽  
Standard Length ◽  
Condition Factor ◽  
Fork Length ◽  
Head Length ◽  
Mean Values ◽  
Snout Length ◽  
Total Length ◽  
Relative Condition Factor ◽  
The Mean

The mean values of total length (75.89 ± 13.09 mm), standard length (54.98 ± 7.07 mm), fork length (60.86 ± 9.14 mm), head length (14.75 ± 2.05 mm), snout length (3.79 ± 0.61 mm), pre-dorsal length (31.53 ± 3.18 mm), height of body (20.2 ± 4.11 mm) and total weight (6.62 ± 3.55g) of combined sex of Puntius chola were calculated. Relationships between total length and standard length, fork length, head length, snout length and pre-dorsal length of Puntius chola were found to be linear, positive and highly significant. The length-weight relationship in male, female and combined sex were determined as Log W=-4.510+2.810 Log L, LogW=-4.204+2.685 Log L and Log W=4.465+2.808 Log L respectively. The mean values of condition factor from observed value (ko) of male, female and combined sex were determined as 1.36 ± 0.089, 1.599 ± 0.181 and 1.515 ± 0.192 respectively. The mean values of condition factor from calculated value (kc) of male, female and combined sex were found to be 1.362 ± 0.054, 1.6 ± 0.124 and 1.511 ± 0.075 respectively. The mean values of relative condition factor of male, female and combined sex were registered as 0.999 ± 0.044 , 0.999 ± 0.064 and 0.999 ± 0.112 respectively. Sex ratio was found to be 1:1. Key words: Standard length; Pre-dorsal length; Puntius chola; Morphomertric; Fish culture. DOI: 10.3329/bjsir.v45i4.7327 Bangladesh J. Sci. Ind. Res. 45(4), 309-314, 2010

Effect of 6-, 12-, and 18-month Photoperiod Cycles on Smolting and Sexual Maturation in Juvenile Atlantic Salmon (Salmo salar)

1992 ◽  
Vol 49 (11) ◽  
pp. 2273-2280 ◽  
Author(s):  
J. Duston ◽  
R. L. Saunders
Keyword(s):  
Atlantic Salmon ◽  
Salmo Salar ◽  
Sexual Maturation ◽  
Condition Factor ◽  
Temperature Cycle ◽  
Frequency Distributions ◽  
Atlantic Salmon Salmo Salar ◽  
Sexually Mature ◽  
Mature Male Parr ◽  
Modal Group

The results support the hypothesis that the commencement of smolting can occur during the decreasing phase of the annual photoperiod cycle, and sexual maturation during the increasing phase of the cycle, provided individuals have attained certain (unknown) growth thresholds. Thereafter the completion of smolting is entrained by the increasing phase of the photoperiod cycle, and sexual maturation by the decreasing phase. Three groups of Atlantic salmon (Salmo salar) were raised in freshwater for over 2 yr from the eyed egg stage under photoperiod cycles of either 6-, 12- (control), or 18-mo periodicity and an ambient 12-mo temperature cycle. Smolting was judged by changes in salinity tolerance and condition factor. All groups developed bimodal length–frequency distributions by December following hatch. Fish continued to be recruited into the upper modal group (UMG) beyond the shortest day of the photoperiod cycle, providing temperature was not limiting growth. The 6-, 12-, and 18-mo photoperiod cycles resulted in approximately 50, 60, and 100% of the populations being recruited into the UMG. Sexually mature male parr (1 + yr old) occurred only in the lower modal group of the 6- and 12-mo groups.

scholarly journals Relationships between fish and otolith dimensions of Pomatomus saltatrix (Linnaeus, 1766) (Perciformes: Pomatomidae) in southeastern Brazil

2019 ◽  
Vol 17 (1) ◽  
Author(s):  
Geysa M. de Souza ◽  
Rafael de A. Tubino ◽  
Cassiano Monteiro-Neto ◽  
Marcus R. da Costa
Keyword(s):  
Food Habits ◽  
Condition Factor ◽  
Specific Model ◽  
Southeastern Brazil ◽  
Length Frequency ◽  
Pomatomus Saltatrix ◽  
Relative Growth ◽  
Frequency Distributions ◽  
Growth Constants ◽  
Species Specific

ABSTRACT The bluefish, Pomatomus saltatrix (Linnaeus, 1766), was used as a species-specific model to study morphometric relationships between otolith size and relative growth variables. Length-weight relationships between Otolith (Length-OL, Height-OH, and Weight-OW) and fish measurements (Total Length-TL and Total Weight-TW) were determined for fishes captured monthly during the year 2015 off the southeastern coast of Brazil. The ANCOVA and Kruskal-Wallis analysis did not indicate significant differences in the relative growth constants between sexes and length frequency distributions (p > 0.05). The condition factor also did not present significant differences between sexes, and right and left otolith measurements (p > 0.05). A total of 398 specimens were sampled: TL = 43.6-67.0 cm, TW = 365-2400 g, OL = 9.65-15.25 mm, OH = 3.65 - 5.45 mm and OW = 0.03-0.11 g. The LWR for grouped sexes was TW = 0.050TL2.55 and otoliths OW = 6.17E-05OL2.59. The best adjustments were TL vs OL (r2 = 0.90); OL vs OW (r2 = 0.90); TW vs OW (r2 = 0.81); and TW vs OL (r2 = 0.80). These results showed that such relationships are helpful tools for predicting the fish size and weight from otoliths, which may be used in food habits and paleontology studies, and other fisheries management applications.

scholarly journals Ecological aspects of Lebiasina erythrinoides (Characiformes: Lebiasinidae) from an andean piedmont stream in Colombia

2016 ◽  
Vol 21 (1) ◽  
pp. 83 ◽  
Author(s):  
Javier Alejandro Maldonado Ocampo ◽  
Alexander Urbano Bonilla ◽  
Jhon Zamudio
Keyword(s):  
Standard Length ◽  
Sexual Maturity ◽  
Condition Factor ◽  
Hydrological Cycle ◽  
Immature Stage ◽  
Minimum Size ◽  
Ecological Aspects ◽  
The Mean ◽  
Reproductive Events ◽  
Reproduction Stage

The present study describes ecological aspects of <em>Lebiasina erythrinoides</em>; 200 individuals were sampled throughout an annual hydrological cycle from October 2008 to September 2009 in La Calaboza stream, a Piedmont tributary of the Rio Cravo Sur. The studied population had more females than males (1.5:1) and preferred habitats dominated by shoreline vegetation and rocky substrates. Prior to reproductive events, individuals presented an increase in the condition factor (K) and the gonosomatic index (GSI). On average, 648.8 oocytes are discharged twice a year: at the beginning of the rainy season, and during falling water phase. The mean sizes at sexual maturity found for females were 73.5 mm standard length (SL) and for males 70 mm SL. Rounding up, an average minimum size of capture of 75 mm SL is proposed. Most specimens of the population (65 %) were found to be maturing or mature (stages II and III), 28.5 % immature (stage I), 5.0 % in post reproduction stage V, and 1.5 % in reproductive phase (IV). Results suggest this species is omnivorous with a preference for invertebrates (IRI = 41.2 %) and vegetal material (IRI = 27.8 %), but also includes a variety of other items. The values of the diet are correlated with hydrological cycle and size.

An ageing methodology, growth parameters and estimates of mortality for hake (Merluccius australis) from around the South Island, New Zealand

1997 ◽  
Vol 48 (3) ◽  
pp. 201 ◽  
Author(s):  
Peter L. Horn
Keyword(s):  
New Zealand ◽  
West Coast ◽  
Growth Parameters ◽  
Length Frequency ◽  
The South ◽  
Female Fish ◽  
The West ◽  
Frequency Distributions ◽  
A Value ◽  
One Year

A method is described to determine the age of hake by counting zones in sectioned otoliths. The technique was validated to age 1 years from the progression of modes in length–frequency distributions, and for ages 2 years onwards by examining the state of otolith margins from fish sampled regularly over a one-year period. von Bertalanffy growth parameters are estimated for hake on the Campbell Plateau and Stewart–Snares shelf, on the Chatham Rise, and off the west coast of the South Island. Hake grow rapidly for about five years, but growth is slight after about 12 years. Female fish have a significantly faster rate of growth than males. A value forM of 0·20–0·25 is proposed. Differences in growth rates and population age distributions imply that there are at least two stocks of hake in New Zealand waters, with fish off the west coast of the South Island being distinct from those on the Campbell Plateau and Chatham Rise.

scholarly journals Some Aspects of the Growth Features and Condition Factor of Arius Gigas (Boulenger, 1911) from Obuama Creek (Rivers State, Nigeria)

2021 ◽  
Vol 23 (2) ◽  
pp. 63-74
Author(s):  
Olaniyi Alaba Olopade ◽  
Henry Eyina Dienye ◽  
Esther Ifeyinwa Nwosu
Keyword(s):  
Condition Factor ◽  
Management Strategies ◽  
Mean Value ◽  
Basic Information ◽  
Allometric Growth ◽  
Length Frequency ◽  
Frequency Distributions ◽  
Biological Features ◽  
Rivers State ◽  
Growth Features

Abstract Length-frequency distributions, length-weight relationships, length-length relationships and condition factors (Fulton’s KF, allometric KA, and relative KR) of Arius gigas in the Obuama Creek in Rivers State, Nigeria were investigated. 217 samples were collected from artisanal fishermen fishing on the Obuama Creek from March to September 2019. The parameter b of the length-weight relationship was 2.52 indicating negative allometric growth. The KF ranged from 0.51 to 2.03 with a mean value of 0.85 ± 0 while the overall low values of KR and KA, in this study are generally a characteristic of fish in poor health. This study provides basic information on some of the biological features of A. gigas which should be useful for facilitating management strategies and regulations of the stocks.

scholarly journals CHANGES IN MORPHOLOGICAL INDEXES OF YOUNG ATLANTIC SALMON (SALMO SALAR L.) EXPOSED TO HEAVY METAL (ZN, CU, NI, CR, PB, CD) MIXTURE: AN EXPERIMENTAL STUDY / ATLANTINIŲ LAŠIŠŲ (SALMO SALAR L.) JAUNIKLIŲ MORFOLOGINIŲ RODIKLIŲ POKYČIAI VEIKIANT SUNKIŲJŲ METALŲ (ZN, CU, NI, CR, PB, CD) MIŠINIU: EKSPERIMENTINIS TYRIMAS

2016 ◽  
Vol 8 (4) ◽  
pp. 411-417
Author(s):  
Gintarė Sauliutė ◽  
Gintaras Svecevičius
Keyword(s):  
Heavy Metals ◽  
Heavy Metal ◽  
Atlantic Salmon ◽  
Salmo Salar ◽  
Condition Factor ◽  
Field Studies ◽  
Morphological Parameters ◽  
One Year ◽  
Somatic Index ◽  
Receiving Water

Morphological indexes are indicative of toxicant effects in fish. Unfortunately, morphological parameters [gill-, liver-, kidney-, viscero-, etc., somatic indexes and the integrated condition factor (CF)], are usually determined in field studies to assess the general fish condition under effect of multicomponent pollution and did not reflect the effects of specific polluting substances (e.g. heavy metals). The purpose of this study was to experimentally evaluate the effect of priority heavy metal model mixture formed based on Maximum-Allowable-Concentration accepted for Lithuanian receiving water bodies (Zn – 0.1, Cu – 0.01, Ni – 0.01, Cr – 0.01, Pb – 0.005 and Cd – 0.005 mg/L, respectively) on condition parameters of one-year-old Atlantic salmon after seven-, fourteen- and twenty eight- day exposure. Significant changes in liver-, kidney- and viscero-somatic indexes were determined, while CF and branchio-somatic-index were found to be not indicative for such kind of the exposure. Correlation analysis between the parameters studied revealed a number of meaningful patterns. The obtained data were compared with the results of the field study in salmonid rivers. Morfologiniai rodikliai – tai toksinio poveikio žuvims indikatoriai. Šie rodikliai (įmitimo koeficientas, visceralinis, žiaunų, kepenų, inkstų ir kt. somatiniai indeksai) paprastai yra taikomi gamtiniuose tyrimuose, norint įvertinti bendrą žuvų fiziologinę būklę, veikiant daugiakomponentei taršai, neišskiriant konkrečių teršalų (pvz., sunkiųjų metalų) poveikio. Šio tyrimo tikslas – eksperimentiškai nustatyti ir įvertinti morfologinių rodiklių pokyčius po 7-ių, 14-os ir 28-ių parų ekspozicijos, veikiant atlantinės lašišos jauniklius prioritetinių sunkiųjų metalų mišiniu esant didžiausioms leistinoms koncentracijoms (DLK), nustatytoms Lietuvos vidaus vandenims: Zn – 0,1; Cu – 0,01; Ni – 0,01; Cr – 0,01; Pb – 0,005 ir Cd – 0,005 mg/l, atitinkamai. Nustatyti visceralinio, kepenų ir inkstų somatinių indeksų žymūs pokyčiai, tačiau įmitimo koeficiento ir žiaunų somatinio indekso pokyčiai buvo nereikšmingi visą ekspozicijos laikotarpį. Ištirtų rodiklių koreliacinė analizė atskleidė keletą svarbių dėsningumų. Gauti duomenys palyginti su gamtinio tyrimo lašišinėse upėse rezultatais.

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